Last week my daughter watched, shaking her head in disbelief, while my bewildered cat followed me up and down the stairs for half an hour. This exercise was the last part of my latest attempt to test fat-busting cosmetic treatments.

I would like to tell you definitively that the two things I tried out - Scala Bio-Fir anti-cellulite lingerie all the way from Brazil, and the Harley Fit Wow Fat Zap "cold" laser treatment - didn't work. With a name like that, the latter really doesn't deserve any credibility at all.

But the truth is, there does seem to have been some reduction in my measurements - a result that I find very confusing.

First the Scala underwear, sold by John Lewis. I had to wear it for at least six hours every day for a month. In practical terms it was a pain - handwashing every night and heaving myself into the control pants, which extended from just under the bra line to just above the knee, every single day during the hottest September on record. The arrival of Scala leggings and tights halfway through the experiment was very welcome: they were much more comfortable, and enabled me to wear something other than trousers.

In all honesty I hated the knickers, and skipped wearing them for a couple of days when I was ill, and one Sunday when I was doing the London Skyride. And they didn't feel like they were doing anything apart from making me uncomfortably hot. If anything the cellulite looked worse, not better.

However, when I measured myself at the end of the month, I had apparently lost one inch off my waist and half an inch off my thighs.

I have to declare here that my food intake was not measured before or during - but I still indulged in wine, chips and chocolate, and my weight has not changed. So where has that reduction come from? Fat compression?

I was even more sceptical about the Fit Wow Fat Zap. The treatment - which is sold by the Harley Fit Clinic in Harley Street, London, plus Selfridges and Harrods (from January) for £2,000 for a block of eight sessions or £350 for individual pay-as-you-go sessions - involves strapping large paddles incorporating cool lasers (as opposed to the "hot" variety used for thread vein and hair removal) to the offending part of your body. For 20 minutes the lasers supposedly zap the fat cells under your skin, making holes in them through which the water, glycerol and free fatty acids can 'spill out'.

You are measured before and after the session, and then immediately do sit-ups and body crunches on a vibrating bed (quite relaxing - I wouldn't mind one at home). Finally, to encourage the fat out of its cosy little cells before the holes close up, you must do half an hour of vigorous exercise within 24 hours of the treatment: hence the running up and down stairs.

I was sceptical about the measurements done by the Harley Fit assistant, who calculated that I had lost a total of seven inches from three different areas of my stomach. But she helpfully marked the points at which she took measurements with pen, so when I got home I re-measured, and discovered that while the bra line was half an inch more than she had found, the belly button one was actually one inch less.

The trouble is, despite the changing measurements, my clothes feel exactly the same and the orange peel effect is still visible.

Go on, say you told me so ... My daughter got in there first: "Surely the exercise is doing you the most good, Mummy. If you did that every day it would be great."

My testing of the Scala lingerie and Fat Zapping laser treatment was hardly scientific. But to have any credence in the scientific and medical world, papers about new procedures or research are normally published in peer-reviewed journals such as the Lancet or British Medical Journal, so they can be scrutinised by those who really have the knowledge to understand the claims.

When I asked John Lewis and The Harley Fit Clinic if such papers had been published in a peer-reviewed journal, John Lewis was unaware of any, and was unable to get in touch with the Brazilian agents before publication. The Harley Fit Clinic provided a copy of Low-Level Laser-Assisted Liposuction, published on Clinics in Plastic Surgery.

But Claire MacEvilly, a nutritionist with the Medical Research Council, points out that this paper is about the use of laser in invasive surgery - where the body has been cut open. She says that for the laser to work through the skin, it would need to be used in collaboration with an electron microscope, so it could be established which cells the laser was hitting.

And the Scala pants - any chance they could reduce cellulite? "I'm afraid not. The only thing that is going to shift cellulite is vigorous exercise," she says. It looks like my daughter was right.

• Jill will be reporting back in two months' time on the efficacy of the Slendertone Face treatment